1. Field of the Invention
This invention relates to a shape production method and apparatus by a window display, and more particularly to a shape production method and apparatus by a window display suitable to compare and examine a plurality of shapes produced in a process of production to modify a shape.
2. Description of Background Art
A method of facilitating modification to a shape produced formerly or production of a similar shape in a designing operation for producing a three-dimensional shape making use of a computer has been proposed. According to a method disclosed in, for example, Japanese Patent Laid-Open No. Hei 8-83296, an operation of a shape is performed in the following procedure. First, when an operation of a shape is performed, in addition to shape data, an operation history including parameters and so forth used for the shape operation is stored together with an ID (identification information). Then, when the shape is to be modified, a parameter in the operation history is changed or part of the operation history is deleted to change the operation history. Finally, a shaping operation is automatically executed in accordance with the changed operation history.
According to the shape production method disclosed in the Japanese Patent Laid-Open document mentioned above, the shape at any point of the shaping operation can be regenerated by tracing the operation history retrospectively. However, since this method regenerates the operation history and actually modifies the shape itself in the current stage based on the history, it cannot satisfy a demand, for example, that a plurality of designers evaluate a plurality of shape plans simultaneously and when necessary to obtain an optimum shape.